1970 C10 Battery/Alternator/External regulator issue
 

I’ve got a ‘70 C10, battery keeps going dead when I’m running lights. Here’s what I’ve gotten so far..

1. Alternator is 2 wire external regulator, running, the battery leads show 12.8 volts, lights on it drops to 12.5V..

2.Battery is new, holding at 13V charged and unhooked.

I need to know, where does the original wiring w the external regulator, the brown wire goes where? The ignition switch? I’ve had overheating issues with the wiring, which is why I don’t currently have it plugged in at #4 on the regulator.

What’s the problem? Alternator or regulator?

Re: 1970 C10 Battery/Alternator/External regulator issue
 

If your alternator is externally regulated you will have more than 2 wires coming off it.

Post up some pics of alt. connections and ext reg. connector. That will help us get you going in the right direction.

Re: 1970 C10 Battery/Alternator/External regulator issue
 

The wiring diagrams are your friend. You need the brown wire hooked up for it to Charge correctly. You need more juice going in the battery while driving than what you are using. So lets use this for a example. Truck running and lights on and radio on. Your using at least 12.5 to 13 volts maybe more depending on the radio and amps you have.
Lets just say 13 volts and the alternator is only charging at 12.5 volts then your not going to keep up and the battery will die. The brown wire shouldn't have anything to do with your truck over heating.

The 2 drawing I posted should be your trucks alternator wiring. The top drawing is stock. The bottom one is with the external regulator jumped and a new internal alternator installed.
:chevy:

Re: 1970 C10 Battery/Alternator/External regulator issue
 

Love the diagrams! Once the brown wire hits the firewall on the top one, where does it connect to?

Re: 1970 C10 Battery/Alternator/External regulator issue
 

It goes to the inside of the cab to the key switch as a resistance wire for ignition power to excite the external voltage regulator/or to the alternator internal voltage regulator, if you have converted.


See the arrows. it is the 24 gauge wire that shares the accessory terminal on the key switch with the large 12 gauge brown wire.


Attachment 1991715

In case you were wondering, the purpose of this wire is provide a 10 ohm resistance to the diode trio in the alternator to protect them from too much current, and to prevent current feedback to the key switch when the key is shut off, which would keep the engine running. It is a backup for the charging light in trucks with the lighted dashes, in case the light bulb burns out.

Re: 1970 C10 Battery/Alternator/External regulator issue
 

Thanks Vett I wasn't sure about it going to the key switch.:chevy:

Re: 1970 C10 Battery/Alternator/External regulator issue
 

Ok, that makes much more sense now Vette. I've been stumped for a while. The initial problem I had, the wiring harness I bought was universal. At one point, I had the brown wire from external regulator up front hooked into the ignition, and that connected to the gauge cluster with the tan wires... long story short, I fried an aftermarket tach, melted another few wires when I was trying to figure out the issue... Its been a nightmare. I thought I had it all figured out when everything stopped smoking and warping, but now, after a short drive with the headlights, the battery discharges and isn't getting charged at all.

Here's my next question then.. can I build a wire with a resistor that can run straight from the #4 blade on the external regulator and plug it into the ignition switch on one of the terminals? If so, which one would be the best one to go with?

Re: 1970 C10 Battery/Alternator/External regulator issue
 

http://67-72chevytrucks.com/vboard/a...6&d=1308289172

this is the setup Im running, without being able to take an actual picture right now. The two pictures are what I have running on the alternator, and the wiring I've used for the regulator, minus the brown wire from #4, and the ignition wiring from american autowire.

The top pic is from a post you had back in 2011, vette.

Re: 1970 C10 Battery/Alternator/External regulator issue
 

I haven't been clear on exactly what you are trying to do. From the picture it looks like you are trying to rewire the external regulator using the stock alternator. If that's the case then it's not going to work. You must get an internally regulated alternator and quit using the external regulator before you can rewire the circuit or you will experience the burnt wires and the other problems you have.
The best thing I recommend for anyone is to just run the brown wire to the new alternator and the red wire which went to the stock regulator, to the new alternator. Then you just have to run the new alternator large output wire to the main junction in your harness where all the circuits feed off from.

When I sat up my new engine, I wired my starter, ignition and charging system so that it would work from the engine bay. I didn't even use the cab circuits at all. The next two diagrams will show you the differences in the alternator wiring and how simple it is.


Here is the stock alternator.

Attachment 1991984



Here is the wiring for the stock alternator:


Attachment 1991980


Here is the internally regulated alternator wiring with the stock regulator removed.

Attachment 1991982


And here is how the alternator is wired and how it looks from the back.

Attachment 1991983


There are newer alternators that will work better but the wiring is a little different at the alternators but is is still easy. The one pictured is the SI model and is the one sold by most alternative suppliers to replace the old stock one. Hope this helps.

Re: 1970 C10 Battery/Alternator/External regulator issue
 

Hey again Vette, sorry I haven't updated in a bit. yes, I'm trying to wire an external regulator. The PO I bought the truck from had the wiring set up for an internal regulated alternator, but a mechanic mentioned to me in a previous setting that it was "magnetized" on the front, which I could verify, and he said that it needed to be replaced. That, in addition to the PO chopping up everything under the sun (horn would honk at any given time, he cut into the pink ignition wire and spliced in a radio), I tried to go back to the stock wiring.

I'm attaching the alternator I have now, in addition to the wiring I have set up (the RF plug I bought had different colored wires, so looking at the back of the alternator, blue from regulator is spliced with black, and white from regulator is spliced with blue). Could you tell me if the alternator is internal or externally regulated? I just bought it from O-O-O, Oreilly, about a week ago because I, in my ignorance, wasn't sure where the problem was.

What I've been able to make out from everything mentioned previously here, is that there isn't a signal from the external regulator to trigger the alternator to charge the battery, giving me the problem of draining the battery when the lights are running. Is that correct?

Following your guidance and rewiring for an internal regulator, and if I jump all the wires like you've graciously shown me, do I need to have a 10 ohm resistance wire going to the ignition switch? And which portion of the ignition switch should that go? To the acc just behind the purple wire?

I really appreciate all your help, you and everyone. I hope this isn't too jumbled and you can make out what I'm trying to get out of my head! hah

Re: 1970 C10 Battery/Alternator/External regulator issue
 

If your going back to stock your missing a wire to the voltage regulator. Its important!

Re: 1970 C10 Battery/Alternator/External regulator issue
 

Thank you Col. Clear as Day! hahaha
That's what I've so diligently been trying to figure out, but I do appreciate your finely honed powers of observation. :metal:

Re: 1970 C10 Battery/Alternator/External regulator issue
 

Did you ever figure out the sensing brown wire for your external regulator? And if so is your charging system work fine or overcharging your system?

Re: 1970 C10 Battery/Alternator/External regulator issue
 

He is missing the brown wire from the firewall to the regulator plug so his alternator will not charge, whereas yours is overcharging. The brown wire is called the exciter wire for the alternator.

Re: 1970 C10 Battery/Alternator/External regulator issue
 

Thanks!!!